How to make a chinese doggy bag?
You could do it this way:


Create a plane and subdivide it twice.
Bring the additional edge loops close to the borders.
Extrude down the whole plane and recalculate the normals with a ctrlN.
Remove the bottom, select the rim and press W > LoopTools > Circle to make your square a circle (if you don't see the LoopTools you need to activate the addon in the Preferences).
Now your bottom is a circle, rotate it on the Z axis so that it's correctly aligned.
If you give your object a Subdivision Surface modifier you'll have a smooth object but your top angles won't be sharp anymore. To sharp then back create some additional edge loops with some ctrl R.
Remove the top faces.
Close the bottom with some extrudes, then a merge: alt M > At Center.
You can add a Solidify modifier to give it thickness.